Base station apparatus and communication method

ABSTRACT

Provided is a base station capable of suppressing increase of overhead of allocation result report in frequency scheduling in multi-carrier communication and obtaining a sufficient frequency diversity effect. In the base station, encoding units ( 101 - 1  to  101 - n ) encode data (# 1  to #n) to mobile stations (# 1  to #n), modulation units ( 102 - 1  to  102 - n ) modulate the encoded data so as to generate a data symbol, a scheduler ( 103 ) performs frequency scheduling according to a CQI from each mobile station so as to uniformly allocate data to the respective mobile stations for a part of RB extracted from a plurality of RB, and an SCCH generation unit ( 105 ) generates control information (SCCH information) to report the allocation result in the scheduler ( 103 ) to the respective mobile stations.

This is a continuation application of application Ser. No. 13/081,727filed Apr. 7, 2011 now U.S. Pat. No. 8,249,013, which is a continuationapplication of application Ser. No. 12/298,707 filed Oct. 27, 2008, nowU.S. Pat. No. 8,077,667, which is a national stage of PCT/JP2007/059089filed Apr. 26, 2007, which is based on Japanese Application No.2006-126454 filed Apr. 28, 2006, the entire contents of each which areincorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a radio communication base stationapparatus and radio communication method used for multicarriercommunication.

BACKGROUND ART

Recently, in radio communication, and mobile communication inparticular, various kinds of information such as image and data inaddition to speech are targeted for transmission. Demands for higherspeed transmission are expected to further increase in the future, andradio transmission techniques that efficiently use limited frequencyresources and realize high transmission efficiency are in demand toperform high speed transmission.

One radio transmission technique that responds to these demands is OFDM(Orthogonal Frequency Division Multiplexing). OFDM is a multicarriertransmission technique of transmitting data in parallel using manysubcarriers, has features such as high-frequency efficiency and reducedinter-symbol interference in a multipath environment, and is known to beeffective in improving transmission efficiency.

Studies are underway to perform frequency scheduling when this OFDM isused in a downlink and data for a plurality of radio communicationmobile station apparatuses (hereinafter simply “mobile stations”) isassigned to a plurality of subcarriers (e.g., see Non-Patent Document1). According to frequency scheduling, a radio communication basestation apparatus (hereinafter simply “base station”) adaptively assignssubcarriers to mobile stations based on received qualities of frequencybands of the mobile stations, so that it is possible to obtain a maximummulti-user diversity effect and perform communication quite efficiently.

Frequency scheduling is generally performed in units of resource blocks(RB's) acquired by making sets of several subcarriers into blocks.Furthermore, there are two assignment methods in frequency scheduling,namely, localized assignment, which is assignment in units of aplurality of consecutive subcarriers, and distributed assignment, inwhich assignment is performed for a plurality of distributedinconsecutive subcarriers.

Furthermore, the assignment result of frequency scheduling performed ina base station is reported to mobile stations using a shared controlchannel (SCCH). Further, studies are underway to report an assignmentresult of the frequency bandwidth of 5 MHz with one SCCH (e.g., seeNon-Patent Document 2).

-   Non-Patent Document 1: R1-050604 “Downlink Channelization and    Multiplexing for EUTRA”, 3GPP TSG-RAN WG1 Ad Hoc on LTE, Sophia    Antipolis, France, 20-21 Jun., 2005-   Non-Patent Document 2: R1-060032, “L1/L2 Control Channel Structure    for E-UTRA Downlink”, NTT DoCoMo, 3GPP TSG-RAN WG1 LTE Ad Hoc    Meeting contribution, 2006/01

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

Here, to improve the frequency diversity effect in distributedassignment, widening the frequency bandwidth targeted for distributedassignment, that is, increasing the number of subcarriers for whichdistributed assignment is performed, is possible. However, an increaseof the number of subcarriers for which distributed assignment isperformed causes an increase of the number of assignment patterns, and,accordingly, more signaling bits are needed to report the assignmentresults. This results in an increase of the overhead for reportingassignment results using SCCH's. As described above, in frequencyscheduling, there is a relationship of trade-off between a frequencydiversity effect and overhead for reporting assignment results.

It is therefore an object of the present invention, according to oneaspect, to provide a base station and a radio communication method forobtaining a sufficient frequency diversity effect in frequencyscheduling while reducing an increase of the overhead for reportingassignment results.

Means for Solving the Problem

The base station of the present invention used in a radio communicationsystem in which a plurality of subcarriers forming a multicarrier signalare divided into a plurality of resource blocks, employs a configurationhaving: a scheduling section that equally assigns data for a radiocommunication mobile station apparatus to partial resource blocksequally extracted from the plurality of resource blocks; a generatingsection that generates control information to report an assignmentresult in the scheduling section to the radio communication mobilestation apparatus; and a transmitting section that transmits the controlinformation to the radio communication mobile station apparatus.

Advantageous Effect of the Invention

According to the present invention, it is possible to obtain asufficient frequency diversity effect in frequency scheduling whilereducing an increase of the overhead for reporting assignment results.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of a base stationaccording to an embodiment of the present invention;

FIG. 2 is a format example of SCCH information according to anembodiment of the present invention;

FIG. 3 is a multiplexing example according to an embodiment of thepresent invention;

FIG. 4 is a block diagram showing a configuration of a mobile stationaccording to an embodiment of the present invention;

FIG. 5 is a PRB extraction example (distributed assignment example 1)according to an embodiment of the present invention;

FIG. 6 is a VRB setting example (distributed assignment example 1)according to an embodiment of the present invention;

FIG. 7 is a signaling bit example according to an embodiment of thepresent invention;

FIG. 8 is a PRB extraction example (distributed assignment example 2)according to an embodiment of the present invention;

FIG. 9 is a VRB setting example (distributed assignment example 2)according to an embodiment of the present invention;

FIG. 10 is a PRB extraction example (distributed assignment example 3)according to an embodiment of the present invention;

FIG. 11 is a VRB setting example (distributed assignment example 3)according to an embodiment of the present invention;

FIG. 12 is a PRB extraction example (distributed assignment example 4)according to an embodiment of the present invention;

FIG. 13 is a VRB setting example (distributed assignment example 4)according to an embodiment of the present invention;

FIG. 14 is a PRB extraction example (distributed assignment example 5)according to an embodiment of the present invention;

FIG. 15 is a VRB setting example (distributed assignment example 5)according to an embodiment of the present invention;

FIG. 16 is a VRB setting example (distributed assignment example 6)according to an embodiment of the present invention; and

FIG. 17 is a frequency scheduling example according to an embodiment ofthe present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, an embodiment of the present invention will be described below indetail with reference to the accompanying drawings.

FIG. 1 shows the configuration of base station 100 according to thepresent embodiment. Base station 100 is a base station used in a radiocommunication system where a plurality of subcarriers forming an OFDMsymbol which is a multicarrier signal are divided into a plurality ofRB's, and performs frequency scheduling using the plurality of RB's.

Base station 100 is configured with encoding sections 101-1 to 101-n andmodulating sections 102-1 to 102-n in association with n mobile stations(MS's) with which base station 100 can communicate.

Encoding sections 101-1 to 101-n perform encoding processing on data #1to #n for mobile stations #1 to #n and modulating sections 102-1 to102-n perform modulation processing on the encoded data to generate datasymbols.

Scheduler 103 performs frequency scheduling based on channel qualityindicators (CQI's) from mobile stations, assigns data for mobilestations to RB's and outputs the data to multiplexing section 104.Examples of a CQI-based scheduling method include the Max CIR method andthe proportional-fairness method. Furthermore, scheduler 103 outputs theassignment results (indicating the data symbols for which mobilestations are assigned to which RB's and subcarriers) to SCCH generatingsection 105.

SCCH generating section 105 generates control information (SCCHinformation) to report the assignment results in scheduler 103 to mobilestations according to the format shown in FIG. 2. In the format shown inFIG. 2, the ID of the mobile station to which a data symbol istransmitted is set in “mobile station ID,” information indicatinglocalized assignment or distributed assignment (e.g., “0” in the case oflocalized assignment, “1” in the case of distributed assignment) is setin “assignment type” and information of a virtual resource block (VRB)assigned to the mobile station is set in “assignment VRB.”

Encoding section 106 performs encoding processing on the SCCHinformation, and modulating section 107 performs modulation processingon the encoded SCCH information and outputs the resulting SCCHinformation to multiplexing section 104.

Multiplexing section 104 multiplexes the data symbols inputted fromscheduler 103, SCCH information and pilots, and outputs the results toIFFT (Inverse Fast Fourier Transform) section 108. Here, themultiplexing of SCCH information and pilots is performed on a persubframe basis as shown in, for example, FIG. 3. FIG. 3 shows a casewhere one subframe is comprised of seven OFDM symbols, and, in thiscase, pilots and SCCH information are mapped to the first and secondOFDM symbols and data is mapped to the third to seventh OFDM symbols.

IFFT section 108 performs an IFFT for a plurality of subcarriers towhich SCCH information, pilots and data, symbols are assigned, togenerate an OFDM symbol which is a multicarrier signal.

CP (Cyclic Prefix) addition section 109 adds the same signal as the rearend part of an OFDM symbol to the head of the OFDM symbol as a CP.

Radio transmitting section 110 performs transmission processing such asD/A conversion, amplification and up-conversion on the OFDM symbol witha CP and transmits the OFDM symbol from antenna 111 to mobile stations.

Radio receiving section 112 receives the CQI's transmitted from mobilestations through antenna 111 and performs reception processing such asdown-conversion and D/A conversion. These CQI's are received qualityinformation reported from the mobile stations. Further, each mobilestation can measure received quality on a per RB basis using thereceived SNR, received SIR, received SINR, received CINR, receivedpower, interference power, bit error rate, throughput and MCS whereby apredetermined error rate can be achieved. Furthermore, the CQI may alsobe referred to as “CSI” (Channel State Information).

Demodulating section 113 performs demodulation processing on the CQI'safter the reception processing, and decoding section 114 performsdecoding processing on the demodulated CQI's and outputs the decodedCQI's to scheduler 103.

Next, FIG. 4 shows the configuration of mobile station 200 according tothe present embodiment.

In mobile station 200, radio receiving section 202 receives the OFDMsymbol transmitted from base station 100 (FIG. 1) through antenna 201,performs reception processing such as down-conversion and D/A conversionand outputs the resulting OFDM symbol to CP removing section 203.

CP removing section 203 removes the CP added to the OFDM symbol andoutputs the resulting OFDM symbol to FFT (Fast Fourier Transform)section 204.

FFT section 204 transforms the OFDM symbol into a frequency domainsignal by performing an FFT on the OFDM symbol, and outputs the SCCHinformation and the data symbols of the signal to equalization section205 and outputs the pilots to channel estimation section 206.

Channel estimation section 206 estimates the channel response on a persubcarrier basis using pilots, outputs the estimation result toequalization section 205, and also measures the received quality of eachRB using the pilots and outputs the measurement result to CQI generatingsection 213.

Equalization section 205 compensates the channel fluctuation of SCCHinformation and data symbols based on the estimation result of thechannel response and outputs the compensated SCCH information and datasymbols to demultiplexing section 207.

Demultiplexing section 207 demultiplexes the SCCH information from thedata symbol and outputs the SCCH information to demodulating section209.

Demodulating section 209 performs demodulation processing on the SCCHinformation, and decoding section 210 performs decoding processing onthe demodulated SCCH information and outputs the decoded SCCHinformation to demultiplexing section 207. Here, SCCH processing section208 is configured with demodulating section 209 and decoding section210.

Further, demultiplexing section 207 extracts only a data symbol directedto mobile station 200 from the data symbols inputted from equalizationsection 205 according to the decoded SCCH information, and outputs theextracted data symbol to demodulating section 211.

Demodulating section 211 demodulates the data symbol inputted fromdemultiplexing section 207 and outputs the demodulated data symbol todecoding section 212.

Decoding section 212 decodes the demodulated data symbol. By this means,received data is obtained.

CQI generating section 213 generates a CQI indicating the receivedquality of each RB measured by channel estimation section 206, andoutputs the CQI to encoding section 214.

Encoding section 214 performs encoding processing on the CQI, andmodulating section 215 performs modulation processing on the encoded CQIand outputs the modulated CQI to radio transmitting section 216.

Radio transmitting section 216 performs transmission processing such asD/A conversion, amplification and up-conversion on the modulated CQI andtransmits the resulting CQI from antenna 201 to base station 100.

Next, a distributed assignment example of frequency scheduling performedin scheduler 103 of base station 100 will be explained in furtherdetail. In the following explanation, assume that an OFDM symbol havinga frequency bandwidth of 10 MHz is comprised of 96 subcarriers andassume a radio communication system in which the 96 subcarriers aredivided into 24 physical resource blocks (PRB's) each containing foursubcarriers.

Distributed Assignment Example 1

In this example, data directed to a mobile station is equally assignedto partial PRB's equally extracted from PRB's 1 to 24.

In this example, as shown in FIG. 5, only the even-numbered PRB's areextracted from PRB's 1 to 24 having a frequency bandwidth of 10 MHz, anda subband for distributed assignment having a frequency bandwidth of 5MHz is formed and set in scheduler 103. By extracting only theeven-numbered PRB's, it is possible to form a subband for distributedassignment comprised of partial PRB's equally extracted from PRB's 1 to24. Further, it is also possible to form a similar subband fordistributed assignment by extracting only the odd-numbered PRB's.

The plurality of PRB's forming a subband for distributed assignment aredivided into VRB's 1 to 12 as shown in FIG. 6. For example, VRB 1 iscomprised of the first subcarriers in PRB's 2, 8, 14 and 20, VRB 2 iscomprised of the second subcarriers in PRB's 2, 8, 14 and 20, VRB 3 iscomprised of the third subcarriers in PRB's 2, 8, 14 and 20, and VRB 4is comprised of the fourth subcarriers in PRB's 2, 8, 14 and 20.Furthermore, VRB 5 is comprised of the first subcarriers in PRB's 4, 10,16 and 22, VRB 6 is comprised of the second subcarriers in PRB's 4, 10,16 and 22, VRB 7 is comprised of the third subcarriers in PRB's 4, 10,16 and 22, and VRB 8 is comprised of the fourth subcarriers in PRB's 4,10, 16 and 22. The same applies to VRB's 9 to 12.

Scheduler 103 assigns one of VRB's 1 to 12 to one mobile station byfrequency scheduling and assigns data for the mobile station to aplurality of PRB's supporting the assigned VRB. For example, whenscheduler 103 assigns VRB 1 to a certain mobile station, scheduler 103assigns the data for the mobile station to the first subcarriers ofPRB's 2, 8, 14 and 20. By such assignment, it is possible to equallyassign data for a mobile station to a plurality of PRB's forming asubband for distributed assignment. Furthermore, scheduler 103 outputsthe assignment result to SCCH generating section 105.

SCCH generating section 105 sets signaling bits associated with theVRB's assigned by scheduler 103 in “assignment VRB” in FIG. 2, accordingto the table shown in FIG. 7. For example, when VRB 1 is assigned to acertain mobile station, SCCH generating section 105 sets “0001” in“assignment VRB.” Furthermore, in this case, SCCH generating section 105sets “distributed assignment” in “assignment type.”

Here, when VRB's are set for all PRB's 1 to 24 as described above, 24VRB's (VRB's 1 to 24) are needed. In this case, the signaling bits shownin FIG. 7 are required for five bits. On the other hand, in the presentexample, VRB's are set for 12 PRB's extracted from PRB's 1 to 24.Therefore, according to the present example, as shown in FIG. 7, thesignaling bits are required for only four bits. Thus, in the presentexample, it is possible to reduce an increase of the number of signalingbits by one bit in assignment for a mobile station. Therefore, in theentire assignment result report, it is possible to reduce an increase ofthe number of signaling bits by the number of bits corresponding to thenumber of mobile stations to which data is assigned.

In the present example, distributed assignment is performed for asubband comprised of partial PRB's which are equally extracted fromPRB's 1 to 24 having a frequency bandwidth of 10 MHz, so that it ispossible to obtain the similar frequency diversity effect as in the casewhere distributed assignment is performed for all of PRB's 1 to 24.

That is, according to the present example, even when the frequencybandwidth targeted for distributed assignment is widened from 5 MHz to10 MHz to improve the frequency diversity effect in distributedassignment, it is possible to obtain a sufficient frequency diversityeffect in frequency scheduling while reducing an increase of theoverhead for reporting assignment results.

Distributed Assignment Example 2

Only the differences between distributed assignment example 2 anddistributed assignment example 1 will be explained below.

As shown in FIG. 8, in the present example, PRB's 1 to 24 having afrequency bandwidth of 10 MHz are divided into two PRB groups eachhaving a frequency bandwidth of 5 MHz. That is, PRB group 1 is comprisedof PRB's 1 to 12 and PRB group 2 is comprised of PRB's 13 to 24.

As shown in FIG. 8, in the present example, only the even-numbered PRB'sare extracted from PRB group 1 and only the odd-numbered PRB's areextracted from PRB group 2, and a subband for distributed assignmenthaving a frequency bandwidth of 5 MHz is formed and set in scheduler103. Even by such extraction method, it is possible to form a subbandfor distributed assignment using partial PRB's equally extracted fromPRB's 1 to 24. Further, it is equally possible to form a similar subbandfor distributed assignment by extracting only the odd-numbered PRB'sfrom PRB group 1 and extracting only the even-numbered PRB's from PRBgroup 2.

A plurality of PRB's forming a subband for distributed assignment aredivided into VRB's 1 to 12 as shown in FIG. 9. For example, VRB 1 iscomprised of the first subcarriers in PRB's 2, 8, 13 and 19, VRB 2 iscomprised of the second subcarriers in PRB's 2, 8, 13 and 19, VRB 3 iscomprised of the third subcarriers in PRB's 2, 8, 13 and 19, and VRB 4is comprised of the fourth subcarriers in PRB's 2, 8, 13 and 19.Furthermore, VRB 5 is comprised of the first subcarriers in PRB's 4, 10,15 and 21, VRB 6 is comprised of the second subcarriers in PRB's 4, 10,15 and 21, VRB 7 is comprised of the third subcarriers in PRB's 4, 10,15 and 21, and VRB 8 is comprised of the fourth subcarriers in PRB's 4,10, 15 and 21. The same applies to VRB's 9 to 12.

Thus, according to the present example, the effects similar to those indistributed assignment example 1 can be obtained.

Distributed Assignment Example 3

In the present example, as shown in FIG. 10, by further dividing PRBgroups 1 and 2 in distributed assignment example 2 into two PRB groupseach having a frequency bandwidth of 2.5 MHz, PRB's 1 to 24 having afrequency bandwidth of 10 MHz are divided into four PRB groups eachhaving a frequency bandwidth of 2.5 MHz. That is, in the presentexample, four PRB groups are formed including PRB group 1-1 comprised ofPRB's 1 to 6, PRB group 1-2 comprised of PRB's 7 to 12, PRB group 2-1comprised of PRB's 13 to 18 and PRB group 2-2 comprised of PRB's 19 to24.

Further, in the present example, one of PRB groups 1-1 and 1-2 isextracted from PRB group 1 and one of PRB groups 2-1 and 2-2 isextracted from PRB group 2, and a subband for distributed assignmenthaving a frequency bandwidth of 5 MHz is formed and set in scheduler103. FIG. 10 shows a case where PRB group 1-1 is extracted from PRBgroup 1 and PRB group 2-1 is extracted from PRB group 2. Here, when PRBgroup 1-1 is extracted from PRB group 1, any of PRB groups 2-1 and 2-2can be extracted from PRB group 2. However, when PRB group 1-2 isextracted from PRB group 1, PRB group 2-2 is extracted from PRB group 2so as not to reduce the frequency diversity effect.

A plurality of PRB's forming a subband for distributed assignment aredivided into VRB's 1 to 12 as shown in FIG. 11. For example, VRB 1 iscomprised of the first subcarriers in PRB's 1, 4, 13 and 16, VRB 2 iscomprised of the second subcarriers in PRB's 1, 4, 13 and 16, VRB 3 iscomprised of the third subcarriers in PRB's 1, 4, 13 and 16, and VRB 4is comprised of the fourth subcarriers in PRB's 1, 4, 13 and 16.Furthermore, VRB 5 is comprised of the first subcarriers in PRB's 2, 5,14 and 17, VRB 6 is comprised of the second subcarriers in PRB's 2, 5,14 and 17, VRB 7 is comprised of the third subcarriers in PRB's 2, 5, 14and 17, and VRB 8 is comprised of the fourth subcarriers in PRB's 2, 5,14 and 17. The same applies to VRB's 9 to 12.

In this way, according to the present example, a subband for distributedassignment is formed in units of PRB groups comprised of a plurality ofconsecutive subcarriers, and consecutive PRB groups are not extracted,so that it is possible to easily perform localized assignment anddistributed assignment at the same time while suppressing a reducedfrequency diversity effect.

Distributed Assignment Example 4

In the present example, as shown in FIG. 12, by further dividing PRBgroups 1 and 2 in distributed assignment example 2 into four PRB groupseach having a frequency bandwidth of 1.25 MHz, PRB's 1 to 24 having afrequency bandwidth of 10 MHz are divided into eight PRB groups eachhaving a frequency bandwidth of 1.25 MHz. That is, in the presentexample, the formed PRB groups are PRB group 1-1 comprised of PRB's 1 to3, PRB group 1-2 comprised of PRB's 4 to 6, PRB group 1-3 comprised ofPRB's 7 to 9, PRB group 1-4 comprised of PRB's 10 to 12, PRB group 2-1comprised of PRB's 13 to 15, PRB group 2-2 comprised of PRB's 16 to 18,PRB group 2-3 comprised of PRBs 19 to 21, and PRB group 2-4 comprised ofPRB's 22 to 24.

Further, in the present example, two PRB groups are extracted from PRBgroups 1-1 to 1-4 of PRB group 1 and two PRB groups are extracted fromPRB groups 2-1 to 2-4 of PRB group 2, and a subband for distributedassignment having a frequency bandwidth of 5 MHz is formed and set inscheduler 103. In this case, a subband for distributed assignment isformed with a combination other than combinations of PRB groups 1-3,1-4, 2-1 and 2-2 so as not to reduce the frequency diversity effect.FIG. 12 shows a case where PRB groups 1-1 and 1-3 of PRB group 1 areextracted and PRB groups 2-2 and 2-4 of PRB group 2 are extracted.

A plurality of PRBs forming a subband for distributed assignment aredivided into VRB's 1 to 12 as shown in FIG. 13. For example, VRB 1 iscomprised of the first subcarriers in PRB's 1, 7, 16 and 22, VRB 2 iscomprised of the second subcarriers in PRB's 1, 7, 16 and 22, VRB 3 iscomprised of the third subcarriers in PRB's 1, 7, 16 and 22 and VRB 4 iscomprised of the fourth subcarriers in PRB's 1, 7, 16 and 22.Furthermore, VRB 5 is comprised of the first subcarriers in PRB's 2, 8,17 and 23, VRB 6 is comprised of the second subcarriers in PRB's 2, 8,17 and 23, VRB 7 is comprised of the third subcarriers in PRB's 2, 8, 17and 23 and VRB 8 is comprised of the fourth subcarriers in PRB's 2, 8,17 and 23. The same applies to VRB's 9 to 12.

In this way, according to the present example, the effects similar tothose in distributed assignment example 3 can be obtained and a subbandfor distributed assignment can be formed with various combinations ofPRB groups.

Distributed Assignment Example 5

In the present example, as shown in FIG. 14, PRB groups 1 and 2 arefurther divided into four PRB groups each having a frequency bandwidthof 1.25 MHz in the same way as distributed assignment example 4.

In the present example, one PRB group is extracted from PRB groups 1-1to 1-4 of PRB group 1 and three PRB groups are extracted from PRB groups2-1 to 2-4 of PRB group 2, and a subband for distributed assignmenthaving a frequency bandwidth of 5 MHz is formed and set in scheduler103. In this case, a subband for distributed assignment is formed with acombination other than combinations of PRB groups 1-4, 2-1, 2-2, 2-3 soas not to reduce the frequency diversity effect. FIG. 14 shows a casewhere PRB group 1-1 of PRB group 1 is extracted and PRB groups 2-1, 2-2and 2-4 of PRB group 2 are extracted.

Further, it is also possible to extract three PRB groups from PRB groups1-1 to 1-4 of PRB group 1 and extract one PRB group from PRB groups 2-1to 2-4 of PRB group 2. However, a subband for distributed assignment isformed with a combination other than combinations of PRB groups 1-2,1-3, 1-4, 2-1 so as not to reduce the frequency diversity effect.

A plurality of PRB's forming a subband for distributed assignment aredivided into VRB's 1 to 12 as shown in FIG. 15. For example, VRB 1 iscomprised of the first subcarriers in PRB's 1, 13, 16 and 22, VRB 2 iscomprised of the second subcarriers in PRB's 1, 13, 16 and 22, VRB 3 iscomprised of the third subcarriers in PRB's 1, 13, 16 and 22, and VRB 4is comprised of the fourth subcarriers in PRB's 1, 13, 16 and 22.Furthermore, VRB 5 is comprised of the first subcarriers in PRB's 2, 14,17 and 23, VRB 6 is comprised of the second subcarriers in PRB's 2, 14,17 and 23, VRB 7 is comprised of the third subcarriers in PRB's 2, 14,17 and 23, and VRB 8 is comprised of the fourth subcarriers in PRB's 2,14, 17 and 23. The same applies to VRB's 9 to 12.

In this way, according to the present example, the effects similar tothose of distributed assignment example 4 can be obtained.

Distributed Assignment Example 6

In the present example, only the even-numbered PRB's are extracted fromPRB's 1 to 24 to form subband 1 for distributed assignment having afrequency bandwidth of 5 MHz (FIG. 6) and only the odd-numbered PRB'sare extracted from PRB's 1 to 24 to form subband 2 for distributedassignment having a frequency bandwidth of 5 MHz (FIG. 16), and thesesubbands are set in scheduler 103. Further, SCCH's 1 and 2 are set inassociation with subbands 1 and 2, respectively. That is, while one SCCHof 5 MHz is used in distributed assignment examples 1 to 5, two SCCH'sof 5 MHz are used in the present example, the assignment result ofsubband 1 for distributed assignment is reported using SCCH 1, and theassignment result of subband 2 for distributed assignment is reportedusing SCCH 2.

A plurality of PRB's forming subband 1 for distributed assignment aredivided into VRB's 1 to 12 as shown in FIG. 6. Likewise, a plurality ofPRB's forming subband 2 for distributed assignment are divided intoVRB's 1 to 12 as shown in FIG. 16.

Scheduler 103 assigns one of VRB's 1 to 12 of subband 1 or 2 fordistributed assignment, to one mobile station by frequency scheduling,and assigns data for the mobile station to a plurality of PRB'ssupporting the assigned VRB. For example, when scheduler 103 assigns VRB1 of subband 1 for distributed assignment to a certain mobile station,scheduler 103 assigns data for the mobile station to first subcarriersof PRB's 2, 8, 14 and 20. Furthermore, for example, when scheduler 103assigns VRB 1 of subband 2 for distributed assignment, to a certainmobile station, scheduler 103 assigns data for the mobile station tofirst subcarriers of PRB's 1, 7, 13 and 19. Scheduler 103 then outputsthe assignment result to SCCH generating section 105.

As described above, SCCH generating section 105 sets signaling bits inassociation with VRB's assigned by scheduler 103, in “assignment VRB” inFIG. 2. For example, when VRB 1 of subband 1 for distributed assignmentis assigned to a certain mobile station, SCCH generating section 105generates SCCH 1 in which “0001” is set in “assignment VRB.”Furthermore, for example, when VRB 1 of subband 2 is assigned to acertain mobile station, SCCH generating section 105 generates SCCH 2 inwhich “0001” is set in “assignment VRB.”

In this way, according to the present example, two subbands fordistributed assignment each having a frequency bandwidth of 5 MHz areformed and assignment results are reported using two SCCH's associatedwith these two subbands for distributed assignment, so that it ispossible to target all PRB's 1 to 24 having a frequency bandwidth of 10MHz for distributed assignment while making signaling bits of “VRBassignment” the same as in distributed assignment examples 1 to 5.

Although a case has been described with the present example where SCCH's1 and 2 set in different frequency bands are associated with subbands 1and 2, respectively, such that subbands 1 and 2 are identified fromSCCH's 1 and 2, it is also possible to add information to identifysubbands 1 and 2, to the SCCH information shown in FIG. 2 to identifysubbands 1 and 2.

Distributed assignment examples 1 to 6 have been explained above.

Next, frequency scheduling will be explained where both distributedassignment and localized assignment are taken into consideration. Here,assume that there are mobile station A to which distributed assignmentis applied and mobile station B to which localized assignment isapplied.

As shown in FIG. 17, for mobile station A, scheduler 103 performsdistributed assignment for arbitrary VRB's in FIG. 6 based ondistributed assignment example 1. Here, assume that a VDRB (VirtualDistributed Resource Block) assigned to mobile station A is comprised offirst subcarriers of PRB's 2, 8, 14 and 20.

On the other hand, for mobile station B, assume that PRB group 1 (FIG.8) defined in distributed assignment example 2 is a subband forlocalized assignment. Further, scheduler 103 performs localizedassignment as shown in FIG. 17. Here, assume that a VLRB (VirtualLocalized Resource Block) assigned to mobile station B is comprised ofPRB's 9, 10 and 11.

In this way, a subband for distributed assignment is formed with PRB'sof 5 MHz equally extracted to obtain a sufficient frequency diversityeffect, while a subband for localized assignment is formed withconsecutive PRB's of 5 MHz to obtain a sufficient frequency schedulingeffect. By this means, it is possible to make the number of signalingbits in the assignment result of distributed assignment the same as thenumber of signaling bits in the assignment result of localizedassignment. Furthermore, when both distributed assignment and localizedassignment are performed at the same time in frequency scheduling, PRB'ssubjected to the distributed assignment are not made to overlap withPRB's subjected to the localized assignment.

The current 3GPP LTE standardization studies the OFDM-based mobilecommunication system in which a plurality of mobile stations havingmutually different frequency bandwidths can be used. More specifically,studies are underway for the mobile communication system having afrequency bandwidth of 20 MHz in which a plurality of mobile stationshaving communication capacities of 10 MHz, 15 MHz and 20 MHz can beused. In such a mobile communication system, a 5 MHz×2 (10 MHz)bandwidth out of the 20 MHz bandwidth is assigned to a mobile stationhaving a 10 MHz communication capacity (10 MHz mobile station), and a 5MHz×3 (15 MHz) bandwidth out of the 20 MHz bandwidth is assigned to amobile station having a 15 MHz communication capacity (15 MHz mobilestation). Furthermore, a mobile station having a 20 MHz communicationcapacity (20 MHz mobile station) can use a 5 MHz×4 (entire 20 MHz)bandwidth. Therefore, taking into consideration that the presentinvention is applied to such a mobile communication system, in thepresent embodiment, the frequency bandwidth of a subband for distributedassignment comprised of partial PRB's is set to 5 MHz. By this means, itis possible to perform the above distributed assignment for a 10 MHzmobile station, 15 MHz mobile station and 20 MHz mobile station.

An embodiment of the present invention has been explained as above.

A mobile station may also be referred to as “UE,” a base stationapparatus as “Node B,” and a subcarrier as “tone.” Furthermore, an RBmay be referred to as “subchannel,” “subcarrier block,” “subband” or“chunk.” Furthermore, a CP may be referred to as “guard interval (GI).”

Furthermore, the assignment result of frequency scheduling may bereported to a mobile station using a physical downlink control channel(PDDCH) instead of an SCCH.

Furthermore, the definition of a subband for distributed assignment maybe set in both a base station and a mobile station beforehand or may bereported from the base station to the mobile station. This report may beperformed using a broadcast channel or the SCCH of each subframe.

Although an example has been described with the above embodiment wherePRB's of 5 MHz are extracted from a frequency bandwidth of 10 MHz, thepresent invention can also be implemented in the same way as above evenwhen PRB's of 10 MHz are extracted from a frequency bandwidth of 20 MHz.

Furthermore, in the above embodiment, although VRB's are set bycombining a plurality of resources obtained by dividing one PRB intofour portions, the number of divisions of one PRB is not limited tofour.

Furthermore, although an example case has been described with the aboveembodiment where even-numbered PRB's or odd-numbered PRB's areextracted, that is, where every second PRB is extracted, every third orevery fourth PRB may be extracted.

Although a case has been described with the above embodiments as anexample where the present invention is implemented with hardware, thepresent invention can be implemented with software.

Furthermore, each function block employed in the description of each ofthe aforementioned embodiments may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC,” “system LSI,” “super LSI,” or“ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells in an LSI can be reconfigured is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to perform functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2006-126454, filed onApr. 28, 2006, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a mobile communication system orthe like.

1. A base station apparatus comprising: scheduler configured to allocateresource blocks with a first allocation or a second allocation to amobile station, wherein resource blocks, each of which is comprised of aplurality of subcarriers that are consecutive in the frequency domain,are divided into the plurality of groups, each of which is comprised ofa predetermined number of resource blocks that are consecutive in thefrequency domain; and radio transmitting section configured to transmit,to the mobile station, control information including both informationdistinguishing between the first allocation and the second allocationand information indicating the resource blocks allocated to the mobilestation, wherein: in the first allocation, the plurality of groups aredivided into a plurality of subsets including a first subset, which iscomprised of at least two of groups that are a part of the plurality ofgroups and that are inconsecutive in the frequency domain, and a secondsubset, which is comprised of at least two of groups that are other thanthe part of the plurality of groups and that are inconsecutive in thefrequency domain, and the resource blocks from one subset selected amongthe plurality of subsets are allocated to the mobile station; in thesecond allocation, the resource blocks are allocated to the mobilestation in units of resource blocks that are consecutive in thefrequency domain; and the information indicating the allocated resourceblocks in the control information has the same number of bits in thefirst allocation and the second allocation.
 2. The base stationapparatus according to claim 1, wherein the control information includesinformation indicating groups including the resource blocks allocated tothe mobile station.
 3. The base station apparatus according to claim 1,wherein, in the first allocation, the control information includesinformation indicating the one subset selected among the plurality ofsubsets.
 4. The base station apparatus according to claim 1, wherein theinformation distinguishing between the first allocation and the secondallocation is represented by 1 bit.
 5. The base station apparatusaccording to claim 1, wherein each of the plurality of groups iscomprised of a same predetermined number of resource blocks.
 6. The basestation apparatus according to claim 1, wherein the predetermined numberis variable.
 7. The base station apparatus according to claim 1,wherein, in the first allocation, the resource block included in each ofall of the at least two of groups is allocated to the mobile station. 8.The base station apparatus according to claim 1, wherein, in the firstallocation, the plurality of groups are divided into the plurality ofsubsets such that the at least two of groups, of which the first subsetis comprised, and the at least two of groups, of which the second subsetis comprised, are formed alternately in the frequency domain.
 9. Thebase station apparatus according to claim 1, wherein, in the secondallocation, the resource blocks that are included in at least one groupof the plurality of groups and that are consecutive in the frequencydomain are allocated to the mobile station.
 10. A communication methodcomprising: allocating resource blocks with a first allocation or asecond allocation to a mobile station, wherein resource blocks, each ofwhich is comprised of a plurality of subcarriers that are consecutive inthe frequency domain, are divided into the plurality of groups, each ofwhich is comprised of a predetermined number of resource blocks that areconsecutive in the frequency domain; and transmitting, to the mobilestation, control information including both information distinguishingbetween the first allocation and the second allocation and informationindicating the resource blocks allocated to the mobile station, wherein:in the first allocation, the plurality of groups are divided into aplurality of subsets including a first subset, which is comprised of atleast two of groups that are a part of the plurality of groups and thatare inconsecutive in the frequency domain, and a second subset, which iscomprised of at least two of groups that are other than the part of theplurality of groups and that are inconsecutive in the frequency domain,and the resource blocks from one subset selected among the plurality ofsubsets are allocated to the mobile station; in the second allocation,the resource blocks are allocated to the mobile station in units ofresource blocks that are consecutive in the frequency domain; and theinformation indicating the allocated resource blocks in the controlinformation has the same number of bits in the first allocation and thesecond allocation.
 11. The communication method according to claim 10,wherein the control information includes information indicating groupsincluding the resource blocks allocated to the mobile station.
 12. Thecommunication method according to claim 10, wherein, in the firstallocation, the control information includes information indicating theone subset selected among the plurality of subsets.
 13. Thecommunication method according to claim 10, wherein the informationdistinguishing between the first allocation and the second allocation isrepresented by 1 bit.
 14. The communication method according to claim10, wherein each of the plurality of groups is comprised of a samepredetermined number of resource blocks.
 15. The communication methodaccording to claim 10, wherein the predetermined number is variable. 16.The communication method according to claim 10, wherein, in the firstallocation, the resource block included in each of all of the at leasttwo of groups is allocated to the mobile station.
 17. The communicationmethod according to claim 10, wherein, in the first allocation, theplurality of groups are divided into the plurality of subsets such thatthe at least two of groups, of which the first subset is comprised, andthe at least two of groups, of which the second subset is comprised, areformed alternately in the frequency domain.
 18. The communication methodaccording to claim 10, wherein, in the second allocation, the resourceblocks that are included in at least one group of the plurality ofgroups and that are consecutive in the frequency domain are allocated tothe mobile station.